NCC Section J Energy Efficiency Explained: Performance Requirements, the DTS Parts J4 to J9, Section J Reports and Lighting Power (2025 Guide)

Section J is the energy efficiency Section of the National Construction Code (NCC). In NCC 2025 Volume One it decides how well a commercial roof, wall and window must insulate, how air-tight the envelope must be, how efficient the air-conditioning and hot water plant must be, and how many watts the lights may draw. It also sets what a building must provide for energy meters, electric vehicle charging and solar panels.

This guide sets out what Section J covers, the four Performance Requirements and the ways to meet them. It then tours the Deemed-to-Satisfy Parts with the key numbers in each. Lighting gets its own section, because its allowance has more moving parts than any other, and the checker in section 7 works it out for a space.

In one minute

• Section J covers Class 3 and Class 5 to 9 buildings and a Class 4 part (Volume One J2D2). A note at the start of Part J1 replaces it for Class 2 buildings with the Section J of the previous edition.

• Four Performance Requirements. J1P1 limits energy use and greenhouse gas emissions, with hourly limits such as 22 kJ/m².hr for an office. J1P2 and J1P3 cover a Class 4 part. J1P4 asks for features that facilitate the later installation of solar, batteries and EV charging.

• Deemed-to-Satisfy or Performance Solution (A2G1(2)). The Deemed-to-Satisfy Provisions are Parts J3 to J9 (J2D1). Part J1 has four Verification Methods for a Performance Solution: J1V1 NABERS Energy, J1V2 Green Star, J1V3 reference building and J1V4 envelope sealing.

• Fabric: a roof Total R-Value of R3.2 to R5.3 by climate zone and class (J4D4). Wall-glazing Total System U-Values from U1.1 to U2.0 (Table J4D6a), and no glazing worse than U5.8 (J4D6(2)).

• Lighting: 4.5 W/m² for an office lit to 200 lx or more and 14 W/m² for retail (Table J7D3a). The allowance rises for small enclosed rooms and for control devices, and the test is the total across the spaces served (J7D3(2)).

1. What Section J applies to

Section J sits in NCC Volume One. Part J1 holds the Performance Requirements and Verification Methods, Part J2 says how the Deemed-to-Satisfy Provisions apply, and Parts J3 to J9 hold them. Specifications 33 to 40, 44 and 46 to 48 carry the calculation rules, such as U-Value and solar admittance (Specification 37) and lighting control devices (Specification 40).

Class 3 and Class 5 to 9 buildings. On the Deemed-to-Satisfy route, J1P1 is met by Parts J4 to J8, the energy monitoring in J9D3 and the solar provisions in J9D5(2) to (4) (J2D2(1)). J1P4 is met by J9D4(1) and (2) and J9D5(1) (J2D2(4)).

A Class 4 part. This is the only dwelling in a Class 5 to 9 building, such as a caretaker's flat (A6G5). Section J treats it much like a house: a house energy rating averaging not less than 7 stars collectively and not less than 6 stars individually (J3D3), or the elemental provisions of Part J3, with its energy usage checked under J3D14 or J3D15 (J2D2(2), (3)). Our NatHERS 7-star guide explains star ratings.

Class 2 buildings. NCC 2025 replaces Section J for them with the Section J of the previous edition. A note at the start of Section J, in Part J1, reads: "For Class 2 buildings, Section J is replaced with Section J of NCC 2022 Amendment 2." So the clauses and numbers in this guide are not the ones for an apartment building.

Variations printed in NCC 2025 change the picture most in three places. New South Wales has its own J1P1 and J1P4, and leaves J1P2 and J1P3 to BASIX. The Northern Territory variation, and a note to Part J1 for Tasmania, replace Section J with the Section J of earlier editions.

Houses (Class 1) are not in Section J. Their energy efficiency rules are in Volume Two Part H6 and Section 13 of the Housing Provisions; our insulation guide for houses covers the R-values.

2. The four Performance Requirements

The Objective is to reduce energy consumption and energy peak demand, reduce greenhouse gas emissions and improve occupant health and amenity (J1O1). The Performance Requirements turn that into four tests.

J1P1, operational energy use and greenhouse gas emissions, applies to every building other than a Class 4 part. It asks for features that facilitate the efficient use of energy and near zero operational emissions. For the conditioned space, the hourly regulated energy consumption and its emissions, averaged over the annual hours of operation, must not exceed these limits.

Building	Energy	Greenhouse gas emissions
Class 6	40 kJ/m².hr	4 g CO2-e/m².hr
Class 5, 7b, 8 or 9a other than a ward area, or a Class 9b school	22 kJ/m².hr	2.2 g CO2-e/m².hr
All other building classifications	8 kJ/m².hr	1 g CO2-e/m².hr

NCC 2025 Volume One J1P1: the hourly limits for the conditioned space.

J1P2 and J1P3 apply only to a Class 4 part. J1P2 caps its heating, cooling and thermal energy loads at the limits in Specification 44. J1P3 caps the energy value of its domestic services at that of 3-star ducted heat pumps, a 5-star instantaneous gas water heater and lighting at 4 W/m².

J1P4, renewable energy, energy storage and electric vehicle charging, requires features that facilitate the future installation of on-site renewable energy generation and energy storage, unless already installed to the maximum practicable extent. It requires the same for electric vehicle charging equipment.

3. The ways to comply

A Performance Requirement is satisfied by a Deemed-to-Satisfy Solution, a Performance Solution, or a combination of the two (A2G1(2)). Figure 1 maps them for Section J.

Deemed-to-Satisfy. J2D1(1) lists the provisions: J2D2, J3D2 to J3D15, J4D2 to J4D7, J5D2 to J5D8, J6D2 to J6D13, J7D2 to J7D9, J8D2 to J8D5 and J9D2 to J9D5. J2D2 then sorts them by class, as section 1 describes. Section 4 walks through them.

Performance Solution. The relevant Performance Requirements are found under A2G2(3) and A2G4(3) (J2D1(2)). One way to show compliance is a Verification Method provided in the NCC (A2G2(2)(b)), and Part J1 has four.

Method	For	What it verifies
J1V1 NABERS Energy	Class 5 offices; Class 3 hotels; Class 6 shopping centres with a gross lettable area over 15 000 m² and air-conditioned common area of at least 20% of it	A NABERS Energy Commitment Agreement of at least 6 stars (office base building), 4 stars (hotels) or 6 stars (shopping centres). The energy model shows at least 6.6, 5.3 or 6.7 stars respectively, plus the comfort conditions and Specification 33.
J1V2 Green Star	Class 3, 5, 6, 7, 8 or 9	Registered for a Green Star Buildings rating and meets its simulation requirements. Annual greenhouse gas emissions less than 90% of the reference building's, a Predicted Mean Vote of −1 to +1 across 95% of the floor area for 98% of the hours of operation, and Specification 33.
J1V3 Reference building	Class 3, 5, 6, 7, 8 or 9	Annual greenhouse gas emissions not more than 97% of a reference building's, modelled with the proposed services. The services' emissions not more than the reference building's services. A comfort or zone load test, and Specification 33. Modelled to Specifications 34 and 48.
J1V4 Envelope sealing	A Class 4 part; Class 5, 6, 8, 9a or 9b other than ward areas in climate zones 1, 7 and 8; Class 3, 9c or 9a ward areas in zones 1, 3, 4, 6, 7 and 8	Air permeability tested by Method 1 of AS/NZS ISO 9972: not more than 10 m³/hr.m² at 50 Pa for a Class 4 part, and 5 m³/hr.m² at 50 Pa for the others.

The Verification Methods of NCC 2025 Volume One Part J1, summarised. J1V1 to J1V3 use a calculation method that complies with ANSI/ASHRAE Standard 140.

4. A tour of the Deemed-to-Satisfy Parts

Figure 2 puts each Part on a building section. The table after it gives the headline numbers, and the paragraphs below fill in the detail.

Part	What it covers	Key numbers
J4 Building fabric	Roofs, ceilings, roof lights, walls, glazing and floors of the envelope	Roof R3.2 to R5.3 (J4D4); roof lights not more than 5% of the floor area and U3.9 (J4D5); wall-glazing U1.1 to U2.0 (Table J4D6a), glazing U5.8 (J4D6(2)); floors R2.0 to R4.75 (Table J4D7)
J5 Building sealing	Chimneys, roof lights, doors, windows, entrances, exhaust fans, construction joints, evaporative coolers	Entrance airlock, self-closing or revolving door with exceptions, including a room of 50 m² or less (J5D5(4)); evaporative cooler damper in zones 4 to 8 (J5D8)
J6 Air-conditioning and ventilation	Controls, fans and ducts, insulation and sealing of ductwork, pumps, pipework, space heating, chillers, unitary plant, heat rejection	Time switch on air-conditioning over 2 kWr and on heaters over 1 kW used for air-conditioning; control dead band not less than 2°C (J6D3)
J7 Artificial lighting and power	Lighting power, lighting controls, display and exterior lighting, boiling and chilled water units, lifts, escalators	Office 4.5 W/m², retail 14 W/m² (Table J7D3a); lift car lights and ventilation off after 15 minutes unused (J7D8)
J8 Heated water and pools	Heated water pipework, gas water heating, swimming pool and spa heating and pumping	Reserved electrical capacity for a heat pump at a COP of 3.25 where water is gas heated (J8D3(3)); pool cover R0.05 (J8D4(2))
J9 Monitoring and energy resources	Energy meters, EV charging, solar photovoltaic and battery provisions	Time-of-use meters over 500 m², sub-metering over 2 500 m² (J9D3); EV boards per Table J9D4; solar per J9D5

The Deemed-to-Satisfy Parts for Class 3 and Class 5 to 9 buildings in NCC 2025 Volume One, with a selection of their numbers.

J4 Building fabric

Part J4 applies to the envelope: the fabric that separates a conditioned space or habitable room from the outside, or from an internal space whose temperature follows outdoor conditions (Schedule 1). Insulation complies with AS/NZS 4859.1 and forms a continuous barrier (J4D3(1)).

The required values are totals, with thermal bridging allowed for. Roofs and floors are calculated with AS/NZS 4859.2, wall-glazing construction with Specification 37 (J4D3(5)). Our rainscreen facade guide shows how far framing can pull a wall's Total R-Value down.

Roofs and ceilings. The minimum Total R-Value depends on the climate zone and on which of two groups the building falls in (J4D4(1)). In zones 7 and 8 it is calculated for an upward direction of heat flow, elsewhere downward. Figure 3 plots both groups. The zone comes from the map in our climate zones guide.

In climate zones 1 to 7 the roof's upper surface must also reflect the sun: a Total Solar Reflectance over 0.55 with a thermal emittance over 0.85, or one of two equivalents (J4D4(2)). Roof lights may total no more than 5% of the floor area of the room they serve, at U3.9 or better (J4D5).

Walls and glazing are assessed together as wall-glazing construction, which excludes display glazing and doors (Schedule 1). Its Total System U-Value must not exceed Table J4D6a (J4D6(1)), and any glazing is capped at U5.8 (J4D6(2)). The wall components need at least R1.0, or the Table J4D6b value where the wall is 80% or more of the area (J4D6(4)). Solar admittance is limited by aspect (J4D6(5)).

Climate zone	1	2	3	4	5	6	7	8
Class 5, 6, 7, 8 or 9b; Class 9a other than a ward area	1.6	1.9	1.7	1.7	1.9	1.8	1.7	2.0
Class 3 or 9c; Class 9a ward area	1.1	1.6	1.2	1.3	1.6	1.6	1.2	1.1

Maximum Total System U-Value of wall-glazing construction (W/m².K), NCC 2025 Volume One Table J4D6a.

Floors need a Total R-Value of R2.0 in climate zones 1 to 7 and R3.5 in zone 8, or R3.25 and R4.75 with in-slab heating or cooling (Table J4D7). A slab-on-ground without in-slab heating or cooling counts as R2.0, with exceptions in zones 7 and 8 (J4D7(2)). A slab-on-ground in zone 8 needs R1.0 edge insulation (J4D7(3)).

J5 Building sealing

Part J5 does not apply to a building in climate zones 1, 2, 3 or 5 cooled only by an evaporative cooler (J5D2(2)). Elsewhere, doors and openable windows are sealed (J5D5(1)). An entrance has an airlock, self-closing or revolving door or the like, with exceptions including an entrance in a room of 50 m² or less (J5D5(4)). Exhaust fans get a self-closing damper (J5D6). An air permeability test under J1V4 is the measured alternative.

J6 Air-conditioning and ventilation

Part J6 is mostly the services engineer's: controls, fans, ducts, pumps, pipework, space heating, chillers, unitary equipment and heat rejection (J6D3 to J6D13). A system must be able to be switched off when its space is unoccupied, with a control dead band of not less than 2°C. Air-conditioning over 2 kWr needs a time switch (J6D3).

J7 to J9: lighting, hot water, meters, EV and solar

J7 is covered in the next section.

J8. Heated water pipework is insulated to J6D9, including 500 mm along each branch line (J8D3(1)). Where water is gas heated, the building reserves the electrical capacity, switchboard space, riser and plant area a later air-source heat pump would need, at a coefficient of performance of 3.25 (J8D3(3)); a Queensland variation leaves this blank. A pool heated by gas or a heat pump needs a cover of at least R0.05 (J8D4(2)).

J9 does not apply within a Class 4 part or to a Class 8 electricity network substation (J9D2).

• Meters. A building or sole-occupancy unit over 500 m² needs time-of-use meters for gas and electricity. Over 2 500 m², air-conditioning, lighting, appliance power, hot water, lifts, renewables, EV charging, batteries and other plant are metered separately, linked to one monitoring interface (J9D3(1) to (3)).

• EV charging. A carpark associated with a Class 3, 5, 6, 7b, 8 or 9 building needs dedicated EV charging distribution boards in each storey, in the number Table J9D4 gives, with a charging control system (J9D4). They are sized for a future 7 kW (32 A) charger in 10% of the spaces for a Class 5 or 6 building, or 20% for a Class 3, 7b, 8 or 9 building (J9D4(2)).

• Battery space. The main switchboard has at least 2 empty three-phase circuit breaker slots and 4 DIN rail spaces labelled for a battery system, unless batteries are installed (J9D5(1)).

• Solar. J9D5(2) describes the on-site solar photovoltaic system two ways. One is roof coverage: 100% of the roof area, less exclusions such as heavily shaded roof, roof pitched over 45°, plant areas and trafficable roofs. The other is a peak output per square metre of conditioned space (Table J9D5a): 65 W/m² for a Class 5, 6 or 7 building in zones 2 to 7, and 40 W/m² for a Class 3 or 9 building there. A building using gas for its services adds the Table J9D5b capacity (J9D5(3)).

5. Lighting power: how J7D3 works

For a building other than a Class 4 part, J7D3(2)(a) sets one test. The aggregate design illumination power load must not exceed the sum of the allowances, each allowance being the area of a space multiplied by its maximum illumination power density in Table J7D3a. The aggregate is the sum of the design loads of the spaces served (J7D3(2)(b)). A space can go over its own allowance if others are under by at least as much.

Illumination power density counts the whole lighting system, including drivers and control devices, but not plug-in desk or floor lamps (Schedule 1).

Space	Maximum IPD (W/m²)
Office artificially lit to an ambient level of 200 lx or more	4.5
Office artificially lit to an ambient level of less than 200 lx	2.5
Board room and conference room	5
Corridors	5
Entry lobby from outside the building	9
Restaurant, café, bar, hotel lounge and a space for serving and consuming food or drinks	14
Retail space	14
School general purpose learning areas and tutorial rooms	4.5
Kitchen and food preparation area	4
Toilet, locker room, staff room, rest room and the like	3
Sole-occupancy unit of a Class 3 or 9c building	5
Health-care: all other patient care areas, including wards and corridors	2.5
Storage	1.5
Carpark, general	2
Carpark entry zone, first 15 m of travel, daytime	11.5
Stairways, including fire-isolated stairways	2
Lift cars	5.5

A selection of the rows in NCC 2025 Volume One Table J7D3a. A space not listed takes a value by its illuminance, from 2 W/m² at 80 lx or less up to 11.5 W/m² for 600 to 800 lx (Note 1). Circulation spaces are included in the allowances (Note 5).

Room aspect. Small and tall enclosed rooms get more allowance. The Room Aspect Ratio is the area divided by the product of the height (floor to the highest part of the ceiling) and the perimeter. Where it is less than 1.5, the maximum IPD may be divided by 0.5 + Room Aspect Ratio/3 (Table J7D3a Notes 2 and 3). A 4 m by 3 m office with a 2.7 m ceiling has a ratio of 12 ÷ (2.7 × 14) = 0.32, a factor of 0.61, and 7.43 W/m² in place of 4.5.

Control devices. In addition, the IPD may be divided by the adjustment factors in Tables J7D3b and J7D3c (Note 4). Table J7D3b covers control devices.

Control device	Where	Factor
Demand-operated controls	Toilet or change room, other than a public toilet, in a Class 6 building	0.4
Demand-operated controls	A group of light fittings serving less than 100 m², controlled by one or more detectors	0.6
Demand-operated controls	A group serving 100 m² or more	0.7
Programmable dimming	At least 75% of the area of a space controlled by programmable dimmers	0.85
Fixed dimming	All fittings	The greater of 0.5 or 0.2 + 0.8L, L being the illuminance turndown
Lumen depreciation dimming	All fittings	0.85
Two-stage sensor, minimum power 30% of peak or less	Fire stairs and other spaces not used for regular transit	0.4
Two-stage sensor, minimum power 30% of peak or less	Transitory spaces in regular use, or a carpark	0.7
Daylight sensor and dynamic lighting control	Lights adjacent windows, in a Class 5, 6, 7, 8 or 9b building or a Class 9a building other than a ward area	0.5
Daylight sensor and dynamic lighting control	Lights adjacent windows, serving a Class 3 or 9c building or a Class 9a ward area	0.75
Daylight sensor and dynamic lighting control	Lights adjacent roof lights, Class 5, 6, 7, 8 or 9b, or 9a other than a ward area	0.6
Daylight sensor and dynamic lighting control	Lights adjacent roof lights, Class 3 or 9c, or a Class 9a ward area	0.8

NCC 2025 Volume One Table J7D3b, in short. The window rows cover lights for a distance from the window equal to the depth of the floor to window head height.

The table's notes carry four rules:

• At most two control device factors can be applied to an area (Note 1).

• Where more than one factor other than room aspect applies, they combine as A × (B/2 + 0.5). A is the lowest factor and B the second lowest (Note 2).

• The dimming and daylight sensor factors do not apply to tungsten, halogen or other incandescent sources (Note 3).

• A daylight sensor factor is only applied between 8:00 am and 7:00 pm (Note 5).

Table J7D3c adds light colour: 0.9 for a colour rendering index of 90 or more, 0.8 for 3500 K or warmer, and 1.1 for 4500 K or cooler, which reduces the allowance.

The controls themselves. J7D4(2) requires all artificial lighting to be on demand-operated controls complying with Specification 40, subject to exceptions. They switch lighting off within 15 minutes of the space being vacated (S40C4(1)), and one control may not operate more than 250 m² of lighting outside a single functional space (J7D4(8)). Lighting by the windows in a Class 5, 6 or 8 building over 250 m² is switched separately, with exceptions (J7D4(9)).

What is not counted. J7D3(3) leaves out, among other things, emergency lighting, display lighting in fixed cabinets, specialist process and performance lighting, and museum display lighting.

A Class 4 part has a simpler rule: not more than 5 W/m² within the unit and 4 W/m² on an attached verandah or balcony, which a Table J7D3b factor may increase (J7D3(1)).

6. What a "Section J report" is

The NCC does not use the term. In practice it is the set of documents that shows the building surveyor or certifier how Section J is met, and its content follows the route.

• Deemed-to-Satisfy: the roof, wall-glazing and floor calculations with thermal bridging (J4D3(5)), the sealing details, the J6 plant and control requirements, the J7D3 lighting power check, the J8 hot water provisions and the J9 meters, EV boards and solar.

• J1V3: an energy model comparing the proposed building with the reference building. It is run with a method complying with ANSI/ASHRAE Standard 140 and Specifications 34 and 48 (J1V3(2)), and the building also complies with Specification 33.

• Performance Solution: A2G2(4) requires a performance-based design brief, the analysis, an evaluation against its acceptance criteria and a final report. The report lists the Performance Requirements and Deemed-to-Satisfy Provisions identified, the Assessment Methods used, confirmation that the Performance Requirement is met, and any conditions or limitations.

Section J does not say who prepares one. Energy efficiency or ESD consultants and building services engineers commonly do. In practice, the certifier decides what evidence it accepts.

7. Check a space's lighting power

Pick the space type, set the room's length, width and ceiling height, and say whether it is enclosed. Then set the number of luminaires and their power with drivers, and the control devices. The plan redraws to scale, and the bars compare the installed power with the allowance. The headline gives the allowance in watts, and the cards show each step with its clause.

8. Worked examples

An open-plan office, 20 m by 20 m, 3.0 m ceiling, lit to 200 lx or more. The base allowance is 400 × 4.5 = 1 800 W. The Room Aspect Ratio is 400 ÷ (3.0 × 80) = 1.67, not under 1.5, so there is no room aspect factor. Motion detectors control groups serving 100 m² or more, a factor of 0.7, so the allowance is 4.5 ÷ 0.7 = 6.43 W/m², or 2 571 W. Fifty 40 W luminaires (2 000 W, 5.0 W/m²) fit, though they would not fit the base allowance.

A small enclosed office, 4 m by 3 m, 2.7 m ceiling. The room aspect factor is 0.61 (section 5), giving 7.43 W/m². With a motion detector for a group under 100 m² (0.6), it becomes 7.43 ÷ 0.6 = 12.38 W/m², or 149 W for the 12 m². Two 40 W luminaires (80 W) leave 69 W.

A perimeter strip with two controls. Along a 30 m facade with a 2.7 m window head, the daylight zone is 30 × 2.7 = 81 m² of office. Its lights have motion detectors for groups under 100 m² (0.6) and daylight dimming by the windows in a Class 5 building (0.5). They combine as 0.5 × (0.6/2 + 0.5) = 0.40, so the allowance is 4.5 ÷ 0.40 = 11.25 W/m², or 911 W. Multiplying the factors instead would give 0.30 and 15 W/m², which Note 2 does not allow.

A shop with its back of house, before any adjustment factors.

• Retail floor: 300 m² at 14 W/m² is 4 200 W; installed 4 250 W, 50 W over.

• Store room: 50 m² at 1.5 W/m² is 75 W; installed 30 W.

• Staff room: 12 m² at 3 W/m² is 36 W; installed 25 W.

The allowances total 4 311 W and the installed loads 4 305 W. The aggregate passes J7D3(2), though the retail floor alone is over.

A 3 000 m² office in climate zone 6. Its roof needs R3.2, where a Class 3 hotel in the same zone needs R4.8 (J4D4(1)). At over 2 500 m², its services are metered separately as well as the building (J9D3(2)).

9. Common mistakes

• Using NCC 2025 Section J for a Class 2 building. A note at the start of Part J1 replaces it for Class 2 buildings. Check which Section J the building is assessed under before any calculation.

• Multiplying lighting factors. Two control factors combine as A × (B/2 + 0.5), not A × B, and no more than two control device factors apply to an area (Table J7D3b Notes 1 and 2).

• Spreading a daylight factor over a whole floor. The window rows cover lights within a depth from the window equal to the floor to window head height. A dimming or daylight sensor factor does not apply to halogen or incandescent lamps (Note 3).

• Failing a design room by room. J7D3(2) compares the aggregate design load with the sum of the allowances. Spare allowance in one space can carry another.

• Quoting the product R-value for the roof. J4D4 sets a Total R-Value, with thermal bridging allowed for under J4D3(5), and in zones 7 and 8 it is for upward heat flow. The batt's label is one layer of it.

10. Where to read the source

NCC 2025 Volume One Section J (Parts J1 to J9), Specifications 33 to 40, 44 and 46 to 48 and A2G1 and A2G2 are free to read on the NCC website. Section J calls up AS/NZS 4859.1:2018 and AS/NZS 4859.2:2018 for insulation and Total R-Value, and AS/NZS ISO 9972:2015 for the air permeability test (Schedule 2). They are purchased from Standards Australia.

Inside AEC Assistant the Code text is searchable by clause, and on a paid plan the Standards are too. Ask what lighting power allowance an open-plan office gets with motion sensors and daylight dimming, and the answer comes back with the clause it was read from. This article is general guidance. The building surveyor or certifier for your project determines compliance.